Kilauea’s lower southwest rift zone near the town of Pahala has been shaken by more than 5,900 earthquakes — most of them magnitude 2 or lower — since August, the U.S. Geological Survey’s Hawaiian Volcano Observatory announced Wednesday.

The largest temblor of 3.5 magnitude occurred on Jan. 6. The quakes have been hitting 15 to 25 miles below the surface and most have not been felt by residents, according to HVO.

Since August, there have been 20 to 40 quakes a day in the region, peaking at more than 80 a day in February. The rates are the highest measured for the area in 60 years of instrument monitoring, HVO officials said.

“Deep earthquakes of this type do not generally pose a hazard from ground-shaking,” HVO said in a statement.

Pahala is more than 50 miles southwest of Pahoa, which is near where Kilauea erupted in Leilani Estates in 2018. Pahala is on the opposite end of Hawaii Volcanoes National Park from Pahoa.

HVO emphasized the clusters of deep earthquakes “in this region does not mean an eruption is imminent. HVO has recorded earthquakes in this area for many decades across several eruptive cycles at both Kilauea and Mauna Loa volcanoes. No correlation between seismic activity in this zone and volcanic activity at the surface has been established, although this is an important topic for future research.”

HVO said the activity since August is likely caused by “transport of magma through the earth’s mantle deep beneath the island, an area that may be the source region supplying magma to the active volcanoes.”

A sustained increase of this deep seismicity above long term background levels began as early as November 2015, although at rates lower than currently observed, HVO officials said. The strongest quake in the region of 4.7 magnitude occurred in January 2006.